When it comes to my neck of the woods one answer: INVASION OF TERRITORY. Copperheads become so infested by multiplying on some people's land, they find their land untenable for other uses. Now they have made a big comeback around my father's rural neighborhood after relatively being rarely seen for the last 20 years. These snakes get under your house, etc. I find the best way is just to throw out mothballs everywhere, they chase off about everything, that way nobody gets mad at you for killing the little snakies.